1. Field of the Invention
The present invention relates generally to surgical cutting instruments having relatively movable inner and outer tubular members and, more particularly, to flexible inner tubular members for being rotatably received in the outer tubular members of surgical cutting instruments and to rotary tissue cutting instruments having flexible inner tubular members rotatably disposed within tubular outer members.
2. Discussion of the Related Art
Surgical cutting instruments in which an elongate inner member is rotated within an elongate, tubular outer member have become well accepted in surgical procedures where access to the surgical site is gained via a narrow portal or passage. Typically, the tubular outer member includes a distal end with an opening defining a cutting port or window and the inner member includes a distal end with a cutting tip for engaging bodily tissue via the opening. Proximal ends of the inner and outer members commonly include hubs which attach to a handpiece having a motor for rotating the inner member relative to the outer member. The distal end of the inner member can have various configurations dependent upon the surgical procedure to be performed, with the opening in the distal end of the outer member being suitably configured to cooperate with the particular configuration of the distal end of the inner member to cut, resect or abrade tissue. Often the inner member is tubular so that the loose tissue resulting from a cutting, resecting or abrading procedure can be aspirated through the lumen of the inner member. It is also common for the direction of rotation of the inner member to be reversible during operation. An example of a rotary tissue cutting instrument of the aforementioned type is described in U.S. Pat. No. 4,203,444 to Bonnell et al for use in performing arthroscopic knee surgery.
The tubular inner and outer members disclosed in the Bonnell et al patent are straight. In many surgical procedures, however, it is desirable for the cutting instruments to be bent or curved to access surgical sites which are generally not accessible with straight cutting instruments. For example, in arthroscopic knee surgery it is well known to use curved cutting instruments which can be positioned at various desired angles relative to the surface of the patella. While rotary tissue cutting instruments with curved or bendable shafts have been used for some time, as exemplified by U.S. Pat. No. 4,466,429 to Loscher et al and U.S. Pat. No. 4,445,509 to Auth, these shafts typically employ a single spirally wound strip of material to impart flexibility while transmitting torque. Unfortunately, spirally wound shafts and couplings tend to unwind when rotated in a direction opposite their winding so that torque can only be transmitted efficiently in one direction.
This problem is addressed in U.S. Pat. No. 177,490 to Fones et al wherein a flexible shaft for transmitting torque in both directions is disclosed having a plurality of coaxial spirally wound strips of material wound in alternating opposite directions relative to one another. U.S. Pat. No. 4,646,738 to Trott describes a rotary tissue cutting instrument for arthroscopic surgery which is similar to the instrument described in the Bonnell et al patent but with a flexible transmission element of the type disclosed in the Fones et al patent. The flexible transmission element of Trott is made up of three coaxial spirally wound strips of material interposed between separate proximal and distal end portions of the inner member to allow the inner member to bend. Proximal and distal end portions of the inner member include reduced diameter neck portions which are telescopically received within the innermost spiral strip to facilitate welding of the strips to the other components of the inner member. Disadvantages of this arrangement include the neck portions tending to stiffen the spiral strips in the vicinity of the cutting tip thereby preventing the inner member from bending adjacent the cutting tip and the inner member having an increased diameter. In addition, it is possible for the separate components to become detached from one another during use such that torque can no longer be effectively transmitted to the cutting tip.
U.S. Pat. No. 5,807,241 to Heimberger discloses a flexible tube, particularly useful as a shank for a flexible endoscope. The flexible tube is formed by cutting a gap in a closed path in a longitudinally straight rigid tube to form interlocking but completely materially or physically separated tube sections that allow the tube to bend axially. The flexible tube may not be well suited for use as a rotatable inner tubular member of a surgical cutting instrument since it may be limited by its torque capabilities to relatively low single direction and bi-direction rotational speeds. Also, it is possible for the individual tube sections to disengage or become detached when the tube is bent.
Accordingly, it is a primary object of the present invention to overcome the abovementioned disadvantages of the prior art and to improve the flexible inner tubular members of rotary tissue cutting instruments used in surgery of the head and neck and other parts of the body.
It is another object of the present invention to reduce the number of parts needed to form a rotatable flexible inner tubular member of a rotary tissue cutting instrument capable of operating at relatively high single direction speeds.
It is yet another object of the present invention to increase the torque capability of a rotatable flexible inner tubular member of a rotary tissue cutting instrument by forming the inner tubular member from a helically or spirally cut tube and at least one helical or spiral wrap applied over the cut region of the tube.
Still another object of the present invention is to facilitate bending of an angled rotary tissue cutting instrument adjacent the cutting tip thereof by forming the inner tubular member from a rigid tube that is cut to form interlocked, helical or spiral tube segments extending in series from a proximal portion of the tube to near the cutting tip and at least one spiral wrap disposed over the tube segments.
A further object of the present invention is to form a rotatable flexible inner tubular member of a rotary tissue cutting instrument from a rigid tube that is cut to form integrally, materially connected tube segments and a spiral wrap disposed over the tube segments.
The present invention is generally characterized in a flexible inner tubular member for being rotatably disposed in an outer tubular member to form a rotary tissue cutting instrument. The flexible inner tubular member is made from a rigid tube having a helical or spiral cut therein extending continuously in a helical or spiral path along the cylindrical wall of the tube and about a central longitudinal axis of the tube. The helical cut extends in the radial direction through the entire thickness of the cylindrical wall to form a plurality of integrally, unitarily connected helical or spiral tube segments creating a bendable region in the tube. The helical cut is formed in a dovetail pattern such that adjacent tube segments present tapered, straight-sided tenons interlocked with tapered, straight-sided mortises. At least a first spiral wrap is disposed over the helical cut and includes a first strip of material helically or spirally wound over the tube segments, with opposite ends of the strip of material being secured to the tube on opposite ends or sides of the helical cut. The helical cut defines an angle with the central longitudinal axis of the tube, and the strip of material is wound over the tube at an angle opposite the angle of the helical cut. A cutting member is disposed at a distal end of the tube. The helical cut and spiral wrap define a flexible region in the inner member to transmit torque as the inner member is rotated within and conforms to the shape of a bent or angled or a longitudinally straight outer tubular member. A second spiral wrap may be disposed over the first spiral wrap and includes a second strip of material spirally wound over the first strip of material, with opposite ends of the second strip of material being secured to the tube on opposite ends or sides of the helical cut. The second strip is wound over the tube at about the same angle and in the same direction as the angle of the helical cut.
Another aspect of the present invention is generally characterized in a rotary tissue cutting instrument including a rigid outer tubular member having open distal and proximal ends and a flexible inner tubular member rotatably disposed in the outer member. The inner member has a cutting member at its distal end, the cutting member being exposed from the distal end of the outer member to cut anatomical tissue as the inner member is rotated within the outer member. In one aspect of the rotary tissue cutting instrument, the outer member has proximal and distal length portions connected by a bend, and the inner member has a flexible region disposed within the bend to allow the inner member to flex or bend as it is rotated in the outer member. The inner member is formed by a rigid tube having a helical or spiral cut, which defines a bendable region, and a spiral wrap disposed over the helical cut. The helical cut extends continuously in a helical or spiral path along a cylindrical wall of the tube and about a central longitudinal axis of the tube. The helical cut extends radially through the entire thickness of the cylindrical wall to form a plurality of integrally, unitarily connected helical or spiral tube segments. The helical cut is formed in a dovetail pattern such that adjacent tube segments are interlocked. The spiral wrap is formed by a first strip of material wound over the tube segments and having its opposite ends secured to the tube. The helical cut and the spiral wrap form the flexible region in the inner member to transmit torque to the cutting member while the inner member conforms to the bend or angle of the outer member as the inner member is rotated in the outer member. In another aspect of the rotary tissue cutting instrument, a second strip of material is wound over the first strip of material and has its opposite ends secured to the tube so that an inner spiral wrap and an outer spiral wrap are disposed over the helical cut. The inner member may be provided with an aspiration port that is exposed from the distal end of the outer member, allowing tissue and fluids to be aspirated from an operative site through the inner member.
Some of the advantages of the present invention are that the number of parts needed to produce a rotary tissue cutting instrument are reduced; the rotary tissue cutting instrument can be bent close to the distal end of the instrument to improve access to an operative site; the size or diameter of the instrument can be minimized to facilitate access to an operative site and expand the areas of use for the instrument; the inner diameter of the inner member can be maximized to enhance aspiration therethrough and minimize clogging; the strength of the flexible inner member is increased; the inner member can be designed for single or bi-directional rotation; disengagement or detachment of adjacent tube segments when subjected to bending forces is deterred; and longitudinal and rotational displacements of the inner tube can be limited or controlled.
Other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings, wherein like parts in each of the several figures are identified by the same reference numerals or by reference numerals having the same last two digits.